Asymmetric catheter curve shapes

ABSTRACT

A deflectable catheter shaft with compression resistance coils is configured to create different curve shapes when the catheter is steered or deflected in different directions. One or more compression resistance coils include an elongated-pitch section. The compression resistance coils may be pull wire compression coils or body compression coils.

BACKGROUND

Field of the Disclosure

The instant disclosure relates generally to a deflectable cathetershaft, and particularly to a catheter shaft with compression resistancecoils configured to create different curve shapes when the catheter issteered or deflected in different directions.

Background Art

Electrophysiology catheters are used in a variety of diagnostic,therapeutic, mapping, and ablation procedures to diagnose and/or correctconditions such as atrial arrhythmias, including, for example, ectopicatrial tachycardia, atrial fibrillation, and atrial flutter. Arrhythmiascan create a variety of conditions including irregular heart rates, lossof synchronous atrioventricular contractions, and stasis of blood flowin a chamber of a heart, all of which can lead to a variety ofsymptomatic and asymptomatic ailments and even death.

Typically, a catheter is deployed and manipulated through a patient'svasculature to the intended site—for example, a site within a patient'sheart or a chamber or vein thereof. The catheter carries one or moreelectrodes that can be used for cardiac mapping or diagnosis, ablationand/or other therapy delivery modes, or both, for example. Once at theintended site, treatment can include, for example, radio frequency (RE)ablation, cryoablation, laser ablation, chemical ablation,high-intensity focused ultrasound-based ablation, microwave ablation,and/or other ablation treatments. The catheter imparts ablative energyto cardiac tissue to create one or more lesions in the cardiac tissueand oftentimes a contiguous or linear and transmural lesion. This lesiondisrupts undesirable cardiac activation pathways and thereby limits,corrals, or prevents errant conduction signals that can form the basisfor arrhythmias.

To position a catheter within the body at a desired site, some type ofnavigation must be used, such as using mechanical steering featuresincorporated into the catheter (or a steerable or fixed-curve introducersheath). In some examples, medical personnel may manually manipulateand/or operate the catheter using the mechanical steering features.

To facilitate the advancement of catheters through a patient'svasculature, the proximal end of the catheter can be manipulated toguide the catheter through a vessels and heart chambers. Thesimultaneous application of torque at the proximal end of the catheterand the ability to selectively deflect the distal tip of the catheter ina desired direction can permit medical personnel to adjust the directionof advancement of the distal end of the catheter and to position thedistal portion of the catheter during an electrophysiological procedure.The distal tip can be deflected by one or more pull wires attached atthe distal end of the catheter that extend proximally to a controlhandle, for example, that controls the application of tension on thepull wire or pull wires.

Two of the mechanical considerations for a catheter shaft are thattransmit torque and resist compression during use. With respect totransmitting torque, medical personnel normally navigate the distal endof the catheter to a desired location in part by manipulating a handledisposed at the proximal end of the catheter shaft, or by rolling theproximal portion of the catheter shaft about its longitudinal axis withtheir fingers. Substantial frictional forces sometimes resisttransmission of torque down the length of the catheter. With respect toresisting compression during use, catheter shafts may includecompression coils that comprise a plurality of stacked coils, such thatthe catheter shaft may be laterally deflected or curved while resistinglongitudinal compression and the concomitant problems that suchlongitudinal compression may cause.

The foregoing discussion is intended only to illustrate the presentfield and should not be taken as a disavowal of claim scope.

BRIEF SUMMARY

Embodiments of the present disclosure include a deflectable cathetershaft with compression resistance coils configured to create differentcurve shapes when the catheter is steered or deflected in differentdirections. One or more compression resistance coils may include anelongated-pitch section. The compression resistance coils may be pullwire compression coils or body compression coils

In accordance with an aspect of the present disclosure a steerablecatheter comprises a proximal catheter shaft section comprising aproximal end and a distal end; a distal deflectable section adjacent tothe distal end of the proximal catheter shaft section, the distaldeflectable section comprising a proximal end and a distal end; a firstcompression coil surrounding a first pull wire and extendinglongitudinally through the proximal catheter shaft section from theproximal end of the proximal catheter shaft section to the proximal endof the distal deflectable section; and a second compression coilsurrounding a second pull wire and extending longitudinally, parallel tothe first compression coil, through the proximal catheter shaft sectionfrom the proximal end of the proximal catheter shaft section to theproximal end of the distal deflectable section; wherein the firstcompression coil comprises a first distal elongated-pitch section.

In accordance with another aspect of the present disclosure a steerablecatheter comprises a proximal catheter shaft section comprising aproximal end, a distal end, and a central lumen; a distal deflectablesection adjacent to the distal end of the proximal catheter shaftsection, the distal deflectable section comprising a proximal end and adistal end; a body compression coil surrounded by the proximal cathetershaft section and extending longitudinally through the central lumenfrom the proximal end of the proximal catheter shaft section to a firstregion at the proximal end of the distal deflectable section; a firstpull wire extending longitudinally through the body compression coilfrom the proximal end of the proximal catheter shaft section to a secondregion at the proximal end of the distal deflectable section, the secondregion being distal to the first region; a second pull wire extendinglongitudinally, parallel to the first pull wire, through the bodycompression coil from the proximal end of the proximal catheter shaftsection to the second region at the proximal end of the distaldeflectable section; and a pull wire compression coil surrounding thefirst pull wire within the body compression coil, the pull wirecompression coil extending longitudinally from the proximal end of theproximal catheter shaft section to the second region at the proximal endof the distal deflectable section.

In accordance with another aspect of the present disclosure a steerablecatheter comprises a proximal catheter shaft section comprising aproximal end and a distal end; a distal deflectable section adjacent tothe distal end of the proximal catheter shaft section, the distaldeflectable section comprising a proximal end and a distal end; acompression coil surrounding a pull wire and extending longitudinallythrough the proximal catheter shaft section from the proximal end of theproximal catheter shaft section to the proximal end of the distaldeflectable section; and wherein the compression coil comprises a distalelongated-pitch section.

The foregoing and other aspects, features, details, utilities, andadvantages of the present disclosure will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a catheter incorporating a deflectablecatheter shaft section in accordance with an embodiment of thedisclosure.

FIG. 2 is a schematic cross-sectional view of the deflectable cathetershaft section of FIG. 1 taken along line 2-2 in FIG. 1, with variouscomponents of the catheter omitted for clarity.

FIG. 3 is a schematic side view of a distal catheter shaft sectionshowing two pull wire compression coils, one with an elongated pitchsection, and showing (in phantom) two possible curve shapes of thedistal catheter shaft section.

FIG. 4 is a schematic cross-sectional view of the proximal cathetershaft section of FIG. 3 taken along line 4-4 in FIG. 3, with variouscomponents of the catheter omitted for clarity.

FIG. 5 is a schematic side view of a distal catheter shall sectionshowing one pull wire compression coil and a body coil, and showing (inphantom) two possible curve shapes of the distal catheter shaft section.

FIG. 6 is a schematic cross-sectional view of the proximal cathetershaft section of FIG. 5 taken along line 6-6 in FIG. 5, with variouscomponents of the catheter omitted for clarity.

FIG. 7 is a schematic, fragmentary side view of a catheter showing twopull wire compression coils, each with a different elongated-pitchsection in the elongated-pitch zone.

FIG. 8 is a schematic, fragmentary side view of a catheter showing twopull wire compression coils, both with a variable pitch in theelongated-pitch zone.

FIG. 9 is a schematic, fragmentary side view of a catheter showing twopull wire compression coils, one of which is discontinuous.

DETAILED DESCRIPTION

FIG. 1 generally illustrates a deflectable electrophysiology catheter 10that comprises a deflectable catheter shaft section or distaldeflectable section 12 in accordance with an embodiment of thedisclosure. Deflectable catheter shaft section 12 comprises an elongatedbody having a distal end 14 and a proximal end 16. In its most generalform, catheter 10 further comprises a tip assembly 18 located at thedistal end 14 of the deflectable catheter shaft section 12, a proximalcatheter shaft section 20 (including a proximal end 57 and a distal end58) located proximal to the proximal end 16 of the deflectable cathetershaft section 12, and a handle assembly 22. Deflectable catheter shaftsection 12 and proximal catheter shaft section 20 can be made ofpolytetrafluoroethylene (PTFE) and may comprise, for example, a PTFEsleeve 60 (see FIGS. 2 and 4). Deflectable catheter shaft section 12 canalso include one or more electrodes, such as ring electrodes 54 and tipelectrode 56, for example. Catheter 10 may be used in any number ofdiagnostic and therapeutic applications, such as the recording ofelectrograms in the heart, the performance of a cardiac ablationprocedure, and other similar applications/procedures.

Still referring to FIG. 1, deflectable catheter shaft section 12 isdisposed between the tip assembly 18 and the proximal catheter shaftsection 20. The length and diameter of the deflectable catheter shaftsection 12 can vary according to the application. Generally, the lengthof the deflectable catheter shaft section 12 can range from about 2inches (50.8 mm) to about 6 inches (152.4 mm) and the diameter of thedeflectable catheter shaft section 12 can range from about 5 French toabout 12 French. The diameter of the deflectable catheter shaft section12 can be about 7 French in accordance with some embodiments of thedisclosure. Although these particular dimensions are mentioned inparticular, the dimensions of the deflectable catheter shaft section 12can vary in accordance with various applications of the deflectablecatheter shaft section 12. The deflectable catheter shaft section 12 canbe configured for deflection independent of, or substantiallyindependent of, the proximal catheter shaft section 20.

FIG. 2 illustrates a schematic cross-sectional view of the deflectablecatheter shaft section 12 taken along line 2-2, as shown in FIG. 1. Inthe illustrated embodiment, the deflectable catheter shaft section 12comprises three substantially separate tubes 26, 30, and 32 forminglumens, each extending along the longitudinal axis of deflectablecatheter shaft section 12. In another embodiment, deflectable cathetershaft section 12 may include fewer or more than three lumens. The lumensof tubes 26, 30, and 32 may extend along the entire length ofdeflectable catheter shaft section 12 or less than the entire length ofdeflectable catheter shaft section 12. Each lumen of tubes 26, 30, 32may be formed to have a predetermined cross-sectional profile and shape.Each lumen of tubes 26, 30, 32 may be lined with liners (not shown),which may be attached to an inner surface of tubes 26, 30, or 32, suchas the inner surface 44 of tube 26, for example. The liners may servethe purpose of providing a lubricious surface (e.g., to allow for thesliding of the pull wires) and insulating the components within thelumens of tubes 26, 30, 32. If provided, the liners may be constructedof a polymeric material, such as polytetraflouroethylene (PTFE) or anyother suitable material. In an embodiment, the PTFE lining is 0.002inches thick and has no impact or minimal impact on the deflection curveof deflectable catheter shaft section 12.

The lumen of tube 26 may be configured to house wiring for electrodes orfor other electrical components. The lumen of tube 26 may also beconfigured for use as an irrigation fluid passageway and the like. Thelumens of tubes 30 and 32, which may be located parallel to and onopposite lateral sides of deflectable catheter shaft section 12, may beconfigured to house pull wires 40 and 42, respectively, to enable thedeflectable catheter shaft section 12 to deflect in two or moredirections. In particular, the handle assembly 22 may comprise at leastone pull wire operatively connected to it to facilitate deflection ofthe deflectable catheter shaft section 12. The pull wires 40, 42 may beformed from a stainless steel (e.g., grades 304 or 316), alloy 35N LT,superelastic nickel-titanium (known as NiTi or Nitinol) wire, carbonfiber, para-aramid synthetic fiber generally available from DuPont underthe brand name KEVLAR®, or other suitable material in accordance withvarious embodiments of the disclosure.

FIG. 3 depicts in solid lines a portion of deflectable catheter shaftsection 12A in an undeflected configuration, and depicts in phantomlines two curved configurations 80, 82 of the deflectable catheter shaftsection when it is fully deflected in opposite directions. The proximalend of deflectable catheter shaft section 12A can include twocompression coils 50 and 52 surrounding pull wires 40A and 42A,respectively. The term “compression coils,” as used herein, means anelongated pull-wire coil comprising (a) at least onelongitudinal-compression-resistant section, including adjacent coilsthat are touching, and also possibly comprising (b) one or moreelongated-pitch sections, each elongated-pitch section includingnon-touching adjacent coils.

Compression coils 50 and 52 may be identical in length and parallel toone another. In an example, compression coils 50 and 52 can be made ofgrade 304 stainless steel rolled flat wire that is about 0.008 inches by0.005 inches. The inner diameter of compression coils 50 and 52 can beabout 0.01 inches and the outer diameter of compression coils 50 and 52can be about 0.02 inches, for example. Compression coil 50, which isassociated with deflection curve 80, can include a distalelongated-pitch section 50′. Compression coil 50 can be attached to thesidewall that also comprises part of deflectable catheter shaft section12A at location 55A via RF bonding, glue, sonic welding, or thermalwelding, for example. In an embodiment, though not shown in FIG. 3,compression coil 50 can optionally be attached to the sidewall that alsocomprises part of deflectable catheter shaft section 12A at location 55Cvia similar attachment means. Compression coil 52 is associated withdeflection curve 82. Compression coil 52 can be attached to the sidewallthat also comprises part of deflectable catheter shaft section 12A atlocation 55D and at location 55B via RF bonding, glue, sonic welding, orthermal welding, for example.

Deflection curve 80 has a radius R1, and deflection curve 82 has aradius R2. In this embodiment, R1 is greater than R2, resulting inasymmetric curve shapes of the deflectable catheter shaft section 12A.When pull wire 42A experiences a longitudinal load (i.e., gets pulledproximally), the deflectable catheter shaft section 12A begins to formthe proximal portion of deflection curve 82 near the distal end ofcompression coil 52, such as between location 55D and the distal end ofcompression coil 52. In contrast, when pull wire 40A experiences alongitudinal load, compression coil 50 allows the deflectable cathetershaft section 12A to begin to form the proximal portion of deflectioncurve 80 near location 55A, adjacent to the proximal end of compressioncoil 50. The elongated-pitch section 50′ of compression coil 50 permitsthe deflectable catheter shaft section 12A to begin curving from a moreproximal location than does compression coil 52 (e.g., location 55Aversus location 55D).

FIG. 4 illustrates a schematic cross-sectional view of the proximal endof the deflectable catheter shaft section 12A taken along line 4-4, asshown in FIG. 3. Lumens formed by tubes 26, 30, and 32 are similar tothose described above with respect to FIG. 2. In addition, compressioncoil 52 is shown surrounding pull wire 42A, and compression coil 50′ isshown surrounding pull wire 40A.

Ha 5 illustrates a portion of a deflectable catheter shaft section 12Band its deflection curves 80′ and 82′ in another embodiment of thepresent disclosure. In this embodiment, a body compression coil 84 issurrounded by the PTFE 60 (not shown in FIG. 5) that may form at leastthe outer material of the deflectable catheter shaft section 12B. Bodycoil 84 encompasses the internal contents of the proximal portion of thedeflectable catheter shaft section 12B. In addition to body coil 84, thepresent embodiment can include compression coil 52 surrounding pull wire42B. No compression coil surrounds pull wire 40B in this embodiment.Body coil 84 can be attached to the sidewall that also comprises part ofdeflectable catheter shaft section 12B at location 55A and/or 55B via RFbonding, glue, sonic welding, or thermal welding, tier example.Compression coil 52 can be attached to the sidewall that also comprisespart of deflectable catheter shaft section 12B at location 55D and,optionally, at location 55B via RF bonding, glue, sonic welding, orthermal welding, for example.

Deflection curve 80′ has a radius R1′, and deflection curve 82′ has aradius R2′. In this embodiment, R1′ is greater than R2′, resulting inasymmetric curve shapes of the deflectable catheter shaft section 12B.When pull wire 42B experiences a longitudinal load, the deflectablecatheter shaft section 12B begins to form the proximal portion ofdeflection curve 82′ near the distal end of compression coil 52, such asbetween location 55D and the distal end of compression coil 52 marked byline 88. In contrast, when pull wire 40B experiences a longitudinalload, body coil 84 allows the deflectable catheter shaft section 12B tobegin to form the proximal portion of deflection curve 80′ near line 86at the distal end of body coil 84. The compression coil 52, in additionto body coil 84, causes the deflectable catheter shaft section 12B tobegin curving from a more distal location than does body coil 84 alone(e.g., line 88 vs line 86).

FIG. 6 illustrates a schematic cross-sectional view of the proximal endof the deflectable catheter shaft section 12B taken along line 6-6, asshown in FIG. 5. Lumens formed by tubes 26, 30, and 32 are similar tothose described above with respect to FIG. 2. In addition, compressioncoil 52 is shown surrounding pull wire 42B, and body coil 84 is shownsurrounding the internal contents of the proximal portion of thedeflectable catheter shaft section 12.

FIG. 7 is a side view of a deflectable catheter shaft section 12Cshowing two pull wire compression coils 90 and 91 surrounding pull wires40C and 42C, respectively. Compression coils 90 and 91 may be identicalin length and parallel to one another. In this embodiment, bothcompression coils 90 and 91 have elongated-pitch sections, 90′ and 91′,respectively, located in an elongated-pitch zone 97. Elongated-pitchzone 97 can have a proximal end 97A and a distal end 97B.Elongated-pitch section 90′ is more elongated, or more stretched out,than elongated-pitch section 91′ in FIG. 7. Consequently, when pull wire40C experiences a longitudinal load, the curve of deflectable cathetershaft section 12C (not shown) may have a larger radius than when pullwire 42C experiences a longitudinal load.

Extrapolating from the example shown in FIG. 7, any combination ofelongated-pitch sections of any pitch size can be substituted for 90′ or91′, thereby creating a plurality of different curve shapes andcurve-shape combinations for a given catheter. This can be beneficialfor creating many different asymmetric or symmetric catheter curveshapes that can be used in a variety of medical procedures and/or with avariety of different anatomies.

FIG. 8 is a side view of a deflectable catheter shaft section 121showing two pull wire compression coils 92 and 92A surrounding pullwires 40D and 42D, respectively. Compression coils 92 and 92A may beidentical in length and parallel to one another. In this embodiment,both compression coils 92 and 92A have elongated-pitch sections, 92′ and92A′, respectively, located in an elongated-pitch zone 97′.Elongated-pitch zone 97′ includes a proximal end 97′A and a distal end97′B. Elongated-pitch sections 92′ and 92A′, which can be identical,have a variable pitch. The variable pitch in this embodiment is agradually elongating pitch moving from the proximal end 97′A to thedistal end 97′B of the elongated-pitch zone 97′. The graduallyelongating pitch can cause deflectable catheter shaft section 12D todisplay symmetric curve shapes upon bending, with increased flexibilitytoward the distal end 14D of deflectable catheter shaft section 12D. Inan embodiment, the durometer of the material (e.g. PTFE) formingdeflectable catheter shaft section 12D can be uniform throughout thelength of deflectable catheter shaft section 12D (rather than graduallydecreasing toward the distal end 14D) because the gradual elongation ofelongated-pitch sections 92′ and 92A′ can provide the requiredflexibility of deflectable catheter shaft section 12D. This can provideadvantages in terms of the cost and ease of manufacturing such cathetershafts.

FIG. 9 is a side view of a deflectable catheter shaft section 12Eshowing two pull wire compression coils 93 and 95 surrounding pull wires40E and 42E, respectively. Compression coils 93 and 95 may be identicalin overall length and parallel to one another. In this embodiment,compression coil 93 includes three sections 93A, 93B, and 93C, separatedby two breaks, 99A and 99B, respectively. This can cause deflectablecatheter shaft section 12E to form a complex curve with bends in twolocations. When pull wire 40E experiences a longitudinal load,deflectable catheter shaft section 12E can form a first bend at or nearthe distal end 93A′ of section 93A. Similarly, when pull wire 40 Eexperiences a longitudinal load, deflectable catheter shaft section 12Ecan form a second bend at or near the distal end 93B′ of section 93B.This can result in deflectable catheter shaft section 12E being capableof forming asymmetric curve shapes, one of which is a complex curve.

Although embodiments of a catheter shaft with compression coils havebeen described above with a certain degree of particularity, thoseskilled in the art could make numerous alterations to the disclosedembodiments without departing from the spirit or scope of thisdisclosure. All directional references (e.g., upper, lower, upward,downward, left, right, leftward, rightward, top, bottom, above, below,vertical, horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentdisclosure, and do not create limitations, particularly as to theposition, orientation, or use of the devices. Joinder references (e.g.,affixed, attached, coupled, connected, and the like) are to be construedbroadly and can include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relationship to each other. It is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative only and notlimiting. Changes in detail or structure can be made without departingfrom the spirit of the disclosure as defined in the appended claims.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

Various embodiments have been described above to various apparatuses,systems, and/or methods. Numerous specific details have been set forthto provide a thorough understanding of the overall structure, function,manufacture, and use of the embodiments as described in thespecification and illustrated in the accompanying drawings. It will beunderstood by those skilled in the art, however, that the embodimentsmay be practiced without such specific details. In other instances,well-known operations, components, and elements have not been describedin detail so as not to obscure the embodiments described in thespecification. Those of ordinary skill in the art will understand thatthe embodiments described and illustrated above are non-limitingexamples, and thus it can be appreciated that the specific structuraland functional details disclosed above may be representative and do notnecessarily limit the scope of the embodiments, the scope of which isdefined solely by the appended claims. 10040 j Reference throughout thespecification to “various embodiments,” “some embodiments,” “oneembodiment,” or “an embodiment,” or the like, means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment. Thus, appearances ofthe phrases “in various embodiments,” “in some embodiments,” “in oneembodiment,” or “in an embodiment,” or the like, in places throughoutthe specification are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments. Thus, the particular features, structures, orcharacteristics illustrated or described in connection with oneembodiment may be combined, in whole or in part, with the features,structures, or Characteristics of one or more other embodiments withoutlimitation given that such combination is not illogical ornon-functional.

It will be appreciated that the terms “proximal” and “distal” have beenused throughout the specification with reference to a clinicianmanipulating one end of an instrument used to treat a patient. The term“proximal” refers to the portion of the instrument closest to theclinician and the term “distal” refers to the portion located furthestfrom the clinician. It will be further appreciated that for concisenessand clarity, spatial terms such as “vertical,” “horizontal,” “up,” and“down” have been used above with respect to the illustrated embodiments.However, surgical instruments may be used in many orientations andpositions, and these terms are not intended to be limiting and absolute.

1. A steerable catheter comprising a proximal catheter shaft sectioncomprising a proximal end and a distal end; a distal deflectable sectionadjacent to the distal end of the proximal catheter shaft section, thedistal deflectable section comprising a proximal end and a distal end; afirst compression coil surrounding a first pull wire and extendinglongitudinally through the proximal catheter shaft section from theproximal end of the proximal catheter shaft section to the proximal endof the distal deflectable section; and a second compression coilsurrounding a second pull wire and extending longitudinally, parallel tothe first compression coil, through the proximal catheter shaft sectionfrom the proximal end of the proximal catheter shaft section to theproximal end of the distal deflectable section; wherein the firstcompression coil comprises a first distal elongated-pitch section. 2.The steerable catheter of claim 1, wherein, when the catheter isdeflected toward the first pull wire, the catheter forms a first curvewith a first radius; wherein, when the catheter is deflected toward thesecond pull wire, the catheter forms a second curve with a secondradius; and wherein the first radius is greater than the second radius.3. The steerable catheter of claim 1, wherein the first distalelongated-pitch section is about 0.25-1.0 inches in length.
 4. Thesteerable catheter of claim 1, wherein the first distal elongated-pitchsection comprises a proximal end and a distal end; wherein the firstcompression coil is secured within the proximal catheter shaft sectionat least at a first location, the first location being at or near theproximal end of the first distal elongated-pitch section; and whereinthe second compression coil is secured within the proximal cathetershaft section at least at a second location, the second location beingparallel to the distal end of the first distal elongated-pitch section.5. The steerable catheter of claim 4, wherein the first and secondcompression coils are secured within the proximal catheter shaft sectionvia at least one of RF bonding, glue, sonic welding, or thermal welding.6. The steerable catheter of claim 1, wherein at least one of the firstcompression coil or the second compression coil comprises two or morediscontinuous sections.
 7. The steerable catheter of claim 1, whereinthe first distal elongated-pitch section comprises a variable pitch. 8.The steerable catheter of claim 7, wherein the first distalelongated-pitch section comprises a proximal end and a distal end; andwherein the variable comprises a progressively elongating pitch longerfrom the proximal end of the first distal elongated-pitch section to thedistal end of the first distal elongated-pitch section.
 9. The steerablecatheter of claim 1, wherein the second compression coil comprises asecond distal elongated-pitch section.
 10. The steerable catheter ofclaim 9, wherein the second distal elongated-pitch section comprises avariable pitch; wherein the second distal elongated-pitch sectioncomprises a proximal end and a distal end; and wherein the variablepitch comprises a progressively elongating pitch longer from theproximal end of the second distal elongated-pitch section to the distalend of the second distal elongated-pitch section.
 11. The steerablecatheter of claim 10, wherein the distal deflectable section comprises asingle-durometer material.
 12. The steerable catheter of claim 1,further comprising a body compression coil surrounded by the proximalcatheter shaft section and extending longitudinally through a centrallumen from the proximal end of the proximal catheter shaft section to afirst region at the proximal end of the distal deflectable section. 13.The steerable catheter of claim 12, wherein, when the catheter isdeflected toward the first pull wire, the catheter forms a first curvewith a first radius; wherein, when the catheter is deflected toward thesecond pull wire, the catheter forms a second curve with a secondradius; and wherein the second radius is greater than the first radius.14. The steerable catheter of claim 1, further comprising a sleevesurrounding the proximal catheter shaft section, wherein the sleevecomprises a material that forms the proximal catheter shaft section. 15.The steerable catheter of claim 14, wherein the material includes PTFE.16-20. (canceled)
 21. The steerable catheter of claim 9, wherein thefirst distal elongated-pitch section has a different pitch than thesecond distal elongated-pitch section.
 22. The steerable catheter ofclaim 9, wherein the first distal elongated-pitch section has the samepitch as the second distal elongated-pitch section.